Musical instrument



July 22, 1941. J. A. KOEHL MUSICAL INSTRUMENT Filed Dec. 7, 1940 2 Sheets-Sheet 1 OOOm mm avm mmwa mink awn ooo oooo oooomoooo oooo OOOO OOOOmOOOO 0000 0000 0000 0000 0000 OOOO OOOOWOOOOMOOOO lnshu R m M w July 22, 1941. J. A. KOEHL MUSICAL INSTRUMENT Filed Dec, 7, 1940 2 Sheets-Sheet 2 SIG/VA L OUTPUT 4/ 6 moan 70R 22% a Patented July 22, 1941 UNITED STATES PATENT OFFICE MUSICAL msraumr James A. K oehl, Chicago, 111. Application December '1, 1m. Serial No. scams (oi. s4 1':1)

This invention relates to piano attachments and has for its primary objects the provision of means for utilizing the playing keys of any standard piano to produce sustained tones.

Another object is to provide a device of the class and for the purpose aforestated which may be readily attached to the piano while in no manner interfering with the ordinary operation of the various mechanisms of the instrument.

A still further object is the provision of a device enabling sustained tones and piano tones to be played at one and the same time when depressing playing keys in the treble and bass res- 'isters respectively of the instrument's keyboard, the forms and arrangement of elements of the device being such that piano tones or sustained tones can be elicited from either of said registers and a change ov fromone register to the other instantly efiecte at the will of the player.

Another object is the provision of a means actuable from the keyboard for selectively rendering the hammers of the piano respectively responsive and non-responsive to depression of the playing keys according as-particular musical effects are desired.

A still further object is to provide an attachment which is selectively actuable to enable the entire keyboard of a piano to be used either for the production of piano tones or sustained tones as desired.

7 Another object is to provide an attachment for pianos. enabling any well known frequency geniiwting devices to be used for the production of sustained tones of any desired timbre.

'f While I prefer to employ means responsive to each individual playing key of apiano for producing a sustained tone of the fundamental pitch of the note associated with said key, whereby and as compared with the frequency range of the short manual of an organ, tones in the frequency range of both said short manual and also the lgp'edal board of the organ can be produced as desired, it shall be understood that I am not to be cally to produce organ tones, thereby economically combining two instruments in one and materially reducing the cost of instruments for the electrical production of sustained tones.

Other objects and advantages will appear from the following description and upon reference to the accompanying drawings, in which:

Figure 1 is a schematic view in top plan illustrating the attachment applied to a piano keyboard;

Figure 2 is a transverse section through a portion of a piano illustrating the application of an electric switch to a playing key and showing the hammer action for said keys and the means for selectively rendering the hammer non-responsive to depression of said key;

Figure 3 is a diagrammatic illustration of the generators for producing complex waveforms of potentials at the tone frequencies of different notes of the musical scale and the switches for rendering said waveforms effective upon an electroacoustic translating device;

Figures 4 and 5 are views partly in transverse section and partly in elevation of a portion of piano keyboard showing a slightly modified form of my invention.

Upon reference to the form of my invention shown in Figures 1-3, inclusive of the accompanying drawings, I represents a conventional piano keyboard comprising eighty-eight playing keys, ranging from note A: below middle 0 to note 0 above middleC. 1

Each individual key 0 of the keyboard I has associated therewith a conventional hammer action I as shown in Figure 2. While my invention is shown applied to a grand piano, this shall not be construed as a limitation. As a matter of fact, in the majority of cases such attachments will be applied to the more commonly used vertical pianos. Between the hammer rail 8 and the butt I of the hammer I0 is a felt covered lifting bar II of a vertically movable yoke II, the longitudinal top bar it of which has wiping engagement with a cam H. Said cam is manually actuable and is mounted upon a rod II which projects forwardly and to the keyboard where it may be conveniently reached by the hand of the player and manipulated. When moved towards the player the cam is retracted from said bar It and the hammer Ills free to be operated in the usual manner. when moved away from the player, the yoke is elevated and the bar ll lifts the hammer to a position where it is non-responsive to the hammer action when the playing key is depressed. I

The damper head II is a part of a conventional damper mechanism which functions in the well-known manner. It will suffice to say that when skillfully used in conjunction with my attachment pleasing musical effects will be produced.

In Figure 3, oscillation generators designated A#:, B2, C and C# are shown. In the instant example, I have stated that my invention is applied to a piano, the keyboard of which has eighty-eight playing keys ranging from note A: in the bass section to note in the treble section. Thus, the bass section embraces thirtynine notes, whereas the treble section embraces forty-nine notes. I make particular reference to this for the reason that for each note in the gamut, I preferably employ an electrical frequency generator which produces a predetermined complex waveform of alternating current of the fundamental pitch of said note. If when translated into sound said waveform of alternating current has the characteristics of an organ tone, it follows that each key of the piano will have at its command two distinct tones, one of which is an actual piano tone produced in response to the hammer action when depressing the key and the other an electrically produced organ tone produced by translating said current into acoustic energy.

Referring now to Figure 1 of the accompanying drawings, the block diagram It represents a frequency generating assembly comprising twelve frequency dividing systems of any well known The entire switch organization is mounted in acasingusecuredatfltothebottomboardll of the piano case 20, and I particularly call attention to the feature of my invention which consists in providing for each playing key of the piano, a vertically movable pin 21 which passes into the case 26 and has its upper felt faced end 21' in yielding engagement with the under surface of the key as shown to advantage in Figure 2. The lower end of the pin passes into the casing 28 and bears freely against the upper construction. Each said system may comprise vacuum tube oscillators, gas content tubes or the equivalent thereof. The systems respectively generating waveforms of alternating current at the tone frequencies of notes A, A#, B and C will each consist of eight individual oscillation generators electrically coupled to one another in cascade fashion by tuned circuits such that their output frequencies are in octave relation. The systems respectively generating frequencies corresponding to notes C#, D, D#, E, F, F#, G and G#, will each thereof consist of seven oscillation generators similarly coupled together in cascade fashion by tuned circuits to secure octave separation of their respective output frequencies. Such frequency dividing systems may themselves be controlled by master oscillators, functioning to impress upon the control grids of the respective first stages, signals which determine the frequency of oscillation of said first stages. As I make no claim to these system apart from their broad combination with other elements of my invention, it will suflice to say that each individual oscillation generator is actuable to deliver a waveform of alternating current to the input circuit of an amplifier upon a circuit being established between said generator and said amplifier. This is accomplished by means of a switch it for and controlled by each individual playing key as shown in Figures 2 and 3, said switch comprising a grounding contact II with which a metallic leaf spring I8 is engaged when the key 6 is elevated, and a contact I! which is engaged by said spring in response to depression of said key. The springs ll of the respective switches I! connect with a common output conductor III of an electroacoustic translating system. The spring ll of each individual switch is connected'by a circuit path It with an oscillation generator producing a frequency corresponding to the note associated with the playing key of which said switch is a part.

face of the free end of the spring II. In this manner and to effect application of my attachment to any well known piano, it is simply required that vertical guide holes 2| be formed in the bottom board ll of the piano case, such that there is one such hole beneath each individual playing key, in each of which is a switch controlling pin 21. By reason of this simple arrangement of the elements no great changes are required to be made to any parts of the piano. The holes are preferably arranged in a longitudinal row in said board 2! of the piano case so as to coincide with a corresponding arrangement of the switch pins 21 and enable free vertical insertion of said pins in their respective holes when securing the casing 23 to the piano.

In Figure 3, it is assumed that the oscillation generator Air: is one of a set of eight similar oscillation generators coupled to each other to secure octave separation of their respective output frequencies. In this manner, frequencies for all the A# notes throughout the gamut of the keyboard are provided. In like manner the Be oscillation generator is one of a set of eight similar oscillation generators which supply frequencies for 111 B notes Similarly, the oscillation generate. C is one of a set embodying eight oscillation generators which furnish frequencies for all of the C notes. The oscillation generator C#, however, is one of a set embodying but seven such oscillation generators. The control grid 20 of each of said oscillation generators is connected with a path 30 which supplies said grid with a controlling signal. A waveform of output voltage from each oscillation generator is adapted to be delivered to a circuit path 3| which connects with the common output conductor 20, the latter connected to the aforementioned translating system ll. Delivery of said output voltage to said common conductor is effected upon close circuiting the key controlled switch It which is individual to said path 3|. In each of said paths 3| is a normally open circuited switch 32. Said switches 32 are arranged in separate banks or gangs, such that there is one such bank or gang of switches for all playing keys in the bass register of the keyboard 5 and one such bank or gang of switches for the-keys in the treble register of the piano. Thus, there will be thirty-nine switches 32 in the bank of switches for the keys in said bass register and 49 such switches in the bank for said treble register. All switches in each said bank of switches are adapted to be simultaneously controlled by a common actuator 33. When the switches are close circuited, output voltagesv from the generators in circuit therewithwill be impressed upon said common output conductor 2| upon close circuiting the switches I. in said paths ii. In Figure 3 wherein four oscillation generators are shown, the generators A#: and B: are associated with keys in the bass register of the keyboard. Generators C and C# are associated with keys in the treble register. Reference is made thereto in order that it will be understood that all generators in any selected register are adapted to be either simultaneously open or ,close circuited in the system according as particular musical results are desired to be obtained. Similarly, there will be two cams I4 and a corresponding number of hammer lifting yokes I! such that one thereof controls all hammers in the bass register and the other all hammers in the treble register.

Having described the essential features of construction of my invention, the operation of the embodiment shown in Figures 1-3, inclusive, is described as follows:

When the instrument is played exclusively as a piano, both b of switches 32 are open circuited. The respective cams it are preferably retrievedfrom their yokes, thereby freeing the hammers Ill. The keys may now be played in the usual manner.

' When the instrument is played as an organ the hammers I are preferably but not necessarily adjusted to render same non-responsive todepression of the playing keys. The switches 32 in both banks of said switches are close circuited. Upon depressing any of the playing keys, paths 3| between respective oscillation generators and the common output conductor 20 will be close circuited in response to actuation of the key switches I6. Waveforms of voltages produced by said generators will be impressed upon the input circuit of the system 2| and translated into sounds which may be sustained as long as the keys are held depressed.

Sustained tones can be played as a melody with the right hand and a piano accompaniment with the left hand. This is accomplished by open circulting the switches 32 in the bass register, .close circuiting the switches 32 in the treble register and preferably but not necessarily adjusting the hammers III in the treble section to render same non-responsive to depression of the playing keys. While I suggest dividing the keyboard into treble and bass sections, in either of which sustained tones may be produced, and whereby a change over from one register can be made as desired, it shall be understood .that in certain embodiments of my invention, the production of sustained tones may and in all probability will be confined to the treble section and may embrace as many octaves as required for given musical results.

New and interesting musical effects are readily obtainable by retrieving the cams I4 and freeing the hammers Illv to render the latter responsive to depression of the playing keys, and close circuiting the switches 32 of either or both banks of said switches. With the elements thus adjusted, the playing keys may be depressed at any desired velocity according as particular musical results are desired to be produced. When the velocity of the keys is low, the piano tones are barely audible. Audibility increases as the key velocity increases. Piano tones and sustained tones are thereby simultaneously producedand by holding the keys depressed after sounding the piano tones, many musically useful effects are had in that sustained tones of the same pitch as the piano tones may be maintained at con- I is within the provih put path II of each generator connects with the screen grid of the generator which supplies a waveform which is rich in harmonics. The path ll, may, however, lead from the plate of the generator and in such event an entirely different waveform of output voltage is had. Any well knownsystem of stops may be connected in the network in which said generators are connected,

whereby any desired waveform of output voltage can be rendered effective upon the system 2|. No claim is made to any of these features as it to employ such stops according as particular timbres are desired to be produced.

While I show oscillators as frequency sources for the production of sustained tones, it shall be understood that this is by way of illustration only and that any well known system can be substituted for said oscillators without departing from the spirit and intention of my invention.

In the form of my invention shown in Figures 4 and 5, I employ for each white key 8a of the jection 38 of the key. A frequency input circuit stant amplitude for any desired interval of time wire 39 is connected to said contact element and as shown said element is normally maintained in an open circuit condition of adjustment by a light spring 40. Upon depressing the key, the element 36 makes electrical contact with an output circuit completing element 311) adapted to be connected to the input of an amplifier as in the first described embodiment of my invention. Switches 35 for all of said white keys are mounted in a small longitudinally disposed casing 4| secured to the piano case as shown;

The black keys la are each provided with a yieldingly depressed element 42 having a contactor 43 adapted to be connected with a frequency generator. The element bears lightly upon the upper face of the black key at the back end thereof and is held in open circuit by the key. In the path of descending motion of the element 42 which motion occurs when depressing key la, is a contact 44 which is-adapted to be connected to the input circuit of said amplifier. Switches for all of said black keys are mounted in a small longitudinally disposed casing 45 upon the case of the piano as shown in Figure 5.

The term vibrators employed in the hereto annexed claims shall mean the strings of the herein disclosed piano or their functional equivalent.

To the best of my knowledge, it is broadly new and novel to combine in a single musical instrument key-controlled means for producing audible ce of anyone skilled in the art equivalents of the mechanical and electrical elements herein employed. v

, In those instances wherein my invention is manufactured as an original part of a piano, the key controlled switches I! can be mounted inside the case of the instrument so as to be responsive to depression of the playing keys. The stop switches 32 may be mounted in any suitable manner upon the case where access can be had thereto as desired.

When the key-controlled switches are mounted as shown in Figure 2, the stop switches 32 may be housed in the casing 28 and the actuators 33 mounted upon the front of said casing where they may be conveniently reached by the player.

What I claim as my invention is:

l. A musical instrument comprising mechanism for producing percussive tones in the pitch relation to notes of the even tempered musical scale, said mechanism including playing keys associated with different notes, and means for producing sustained tones in the same pitch rela-- tion as said percussive tones and including mechanism related to and responsive to depression of any playing key for rendering effective upon an electrical sound producer a waveform of alternating current having the tone frequency of the note associated with said key and for sustaining the resultant tone for such interval of time as the key shall remain depressed.

2. A musical instrument comprising vibrators adapted respectively to produce complex waveforms of audible vibrations at the tone frequencies of different notes of the musical scale, electrical generators respectively producing complex signals at the fundamental frequencies of said audible vibrations, means for translating said signals into audible sounds, an actuator for each individual vibrator, a playing key for operating said'actuator, and an electric switch also actuable by said key for close circuiting said translating means with a generator producing a signal having the frequency of the note associated with said key.

3. A musical instrument comprising vibrators adapted respectively to produce. audible vibrations at the tone frequencies of different notes of a musical scale, electrical generators respectively producing tone signals at the same fundamental frequencies as said audible vibrations, playing keys, such that there is one such key for each of said notes, means for translating said signals into sounds, and respective means for and actuable by and upon depression of the key at low velocity for close circuiting said translating means with a generator producing a signal having the vibration frequency of the note associated with said key and actuable upon the velocity being increased to cause an audible vibration of the frequency of said note to speak during translation of said signal into audible sound.

4, A musical instrument comprising vibrators adapted respectively to produce complex wavecies of different notes of the musical scale, electrical generators respectively producing signals at the fundamental tone frequencies of said audible vibrations, means for translating said signals into audible sounds, an actuator for each individual vibrator, a playing key for operating said actuator, an electric switch also actuable by said key for close circuiting said translating means with a generator producing a signal having the frequency of the note associated with said key, and means for selectively rendering the actuators inactive relative to said vibrators upon depressing said playing keys.

5. In a musical instrument employing playingkey-controlled vibrators respectively producing audible vibrations at the tone frequencies of different notes of the musical scale, and an electroacoustic translating means, electrical generators respectively producing signals at the frequencies of said audible vibrations, means for and controlled by each playing-key upon depression thereof for close circuiting said translating means with a generator producing a signal at the tone frequency of the note associated with said key, and means selectively actuable to render the vibrators non-responsive to deprusion of said keys.

6. In a musical instrument employing P ayingkeys associated with diflerent notes of the musical scale, vibrators actuable in response to depression of said keys and respectively producing audible vibrations at the tone frequencies of said notes; an electro-acoustic translating system. electrical sources respectively supplying tone signals "at the frequencies of said audible vibrations; means selectively actuable to render the vibrators non-responsive to depression of said keys, and means responsive to depression of selected keys for rendering signals at the frequencies of notes associated with said keys eifective upon'said translating means throughout such period of time that said keys shall remain depressed.

7. The combination with a musical instrument having a keyboard, the playing keys of which are associated with different notes of a musical scale, and means individual to and actuable by each playing key for producing a percussive sound of the frequency of the note associated with said key, of mechanism for each individual playing key for electrically generating a signal of the same frequency as the percussive sound produced by the same key, and means in coaction with the signal generating mechanism and said key for converting said signal into sound to produce with said percussive sound a timbre which is a mixture of the two sounds.

8. The combination with a musical instrument having a keyboard, the playing keys of which are associated with different notes of a musical scale, and means individual to and actuable by each playing key for producing a percussive sound of the frequency of the note associated with said key, of mechanism for each individual playing key for electrically generating a signal of the same frequency as the percussive sound produced by the same playing key, and selectively active means in coaction with the signal generating mechanism and said key for convertingsaidsignal into soundtoproduce with said percussive sound a timbre which is a mixture of the two sounds. c

9. The combination with a musical instrument having a keyboard. the n -r keys of forms of audible vibrations at the tone frequenwhich are associated with different notes of a a,aso,oos

musical scale, and means individual to and actuable by each playing key for producing a percussive sound of the fundamental frequency of the note associated with said key, of mechamm for each individual playing key for elec- .6

trically generating a signal of the same frequency as the percussive sound produced by the same key; means in coaction with said signal sive sound a timbre comprising a mixture of the two sounds, and meansfor controlling the. amplitude of one of said sounds relative to that of the other sound.

10. The combination with a musical instrument having a keyboard, the playing keys of which are associated with different notes of a musical scale, and means individual to and actuable by each playing key for producing a percussive sound of the frequency of the note associated with said key; of mechanism for each individual playing key for electrically generating a signal of the same fundamental frequency as the percussive sound produced by the same key; means in coaction with said signal generating mechanism and said key and actuable by the latter for converting said signal into sound to produce a timbre comprising a mixture of both said sounds, and means for controlling the amplitude of one of said sounds relative to that of the other sound, said key actuable means serving to sustain said one sound-as long as playing pressure is applied to said key.

11. The combination with a musical instrument having a keyboard, the playing keys of which are associated with different notes of a musical scale, and means individual to and actuable by each playing key for producing a percussive tone of the frequency of the note associated with said key; of mechanism also actuable by each individual playing key for electrically generating a signal having the frequency,

of the note associated with said key and a waveform different from that of the percussive tone produced by the same key, and means for rendering said signal effective upon an electrical sound producer to produce a tone simultaneously with production of said percussive tone and provide therewith a timbre which is a combination of both said tones.

12. In a musical instrument for producin musical sounds of diflerent timbre, some of which have natural periods of decay, a keyboard; means actuable from the keys of said keyboard for mechanically producing musical sounds having the aforementioned natural periods of decay; mechanism actuable from the keys of said keyboard for electrically producing sounds of the same pitch as sounds being mechanically produced at any instant; and means associated with and controlled by said keys for sustaining said electrically produced sounds as long"-as desired after decay of mechanically produced sounds of the same pitch.

13. In a musical instrument, a keyboard, mechanism actuable from the keys of said keyboard for producing piano tones bearing the pitch relation to musical notes associated with different keys of said keyboard; and means for enriching said piano tones. said enriching means comprising a generator of alternating current for each individual key of said keyboard, the waveform of said alternating current having a higher harmonic content than that of the piano tone produded by the same key a nd being of the same frequency as said piano tone. electroacoustic mechanism for translating said current into sound, and means associated with and controlled by the keys of said keyboard for sustaining sound produced by the translating mechanism as long as desired.

14. Inc combination with a piano having a keyboard and means associated with each individual key thereof for producing a tone of-the frequency of the note associated therewith, of a generator of alternating current associated with each individual key of said keyboard for continuously producing alternating current of the frequency of the note associated with said key but of a waveform different from that of the piano tone produced by the same key, and means enabling selective conversion of said alternating currents into sounds.

15. In a musical instrument, the combination with a piano having a keyboard and means actuable by each individual key thereof for producing a piano tone of the frequency of thenote 1 associated with said key, of an electroacoustic translating device, means including pulsation generators for generating waveforms of voltages at the frequencies of notes associated with different keys of said keyboard and actuable when depressing selected keysto render said waveforms effective upon said translating device to produce sounds of the same frequencies as the notes associated with said keys, mechanism for preventing translation of certain of said voltages keyboard and means actuable therefrom for producing piano tones in the pitch relation to musical notes associated with different keys thereof,

of an electroacoustic translating device; a generator of alternating current for each individual playing key of said keyboard for continuously producing alternating current of the fundamental frequency of the piano tone associated with said key and waveform difl'erent from that of said piano tone and adapted upon depression of said key to actuate said translating device and effect production of sound during production of a piano tone by said key, and means for sustaining the sound produced by the translating device as long as desired and at any selected amplitude.

17. The combination of a musical instrument employing a keyboard and mechanism actuable by the different keys thereof for mechanically producing musical sounds having natural periods of decay and pitches corresponding to notes of a musical scale associated with said keys; and mechanism for generating and converting alternating voltages into sounds, said mechanism including a generator for and associated with each individual playing key of said keyboard for continuousLv producing alternating voltage of the 7 tone frequency as the note associated with said keyboard for producing an audible sound of the tone frequency oi the note associated with said key, and meansassociabd with and operating in response to each successive depression 01 a key for setting a respective vibratile member in vibration, and continuously operating mechanisms, one for each playing key 0! said keyboard, for electrically producing a signal 0! the pitch oi the note associated with said key and including means associated with and responsive to actuation of the key for eflecting conversion of said signal into sound and for continuing said conversion as long as the key remains depressed.

19. A musical instrument having a keyboard, means individual to each playing key of said keyboard for producing a piano tone of predeter v mined frequency; means also individualto each of said playing keys ior electrically producing a tone signal of the frequency of the pianotone associated with the same key; an electrical sound producer for conversion 0! said signals into audible sounds; and mechanisms actuable to render either the first or second-named means active independent of the other for the production of sounds when playing selected playing 20. A musical instrument having a keyboard. means individual to each playing key or said keyboard for producing a piano tone of predetermined irequency, means also individual to each of said playing keys for electrically producing a tone signal 01' the frequency of the piano tone associated with the same key, an electrical sound producer for conversion of said signals into audible sounds, and mechanisms selectively otsaidplayingkeys iorelectricaliyproducingatone signal of the frequency 0! the piano tone associated with the same key, an electrical sound producer ior conversion oi said signals into audible sounds, and mechanisms selectively actuable to render either the first or secondnamed means active tor the production of count when playing keys of a selected portion oi the keyboard.

22. A musical instrument having means, including a keyboard, for producing piano tones in the pitch relation to musical notes associated with the diil'erent playing keys oi said keyboard, and means for producing waveforms of alternating voltages in the same pitch relation as the aiorementioned piano tones and oi the timbre oi organ tones and ior converting same into audible sounds, said second-named means associated with and coacting with said first-named means and both said means associated with the keys 0! 'said keyboard so that each individual key has at its command a piano tone and an organ tone of the same pitch when playing any selected keys 01! said keyboard.

23. A musical instrument having means, in-

cluding a keyboard, (or producing piano tones in. the pitch relation to musical notes associated actuahle to render the first and second-named means independently or coniointly active for the production of sounds when playing selected play- 21. a musical instrument having a keyboard.

with the diflerent playing keys of said keyboard, and means for producing waveforms of alternating voltages in the same pitch relation as the aforementioned piano tones and of the timbre of organ tones and for converting same into audible sounds, said second-named means associated withand coacting with saidiirst-named means and both said means associated with the keys of said keyboard so that each individual key hasat its commandapiano tone andanol'II-n tone 0! the same pitch when playing any selected keys oi said keyboard, and means selectively actuable to render the instrument operable ior the exclusive production of tones of either of said timbres.' 1

JAMES A. KOEHL 

